Update AGENTS.md files across multiple modules to standardize task status update instructions and introduce a new document for Secret Leak Detection operations.

- Modified task status update instructions in AGENTS.md files to refer to corresponding sprint files as `/docs/implplan/SPRINT_*.md` instead of `docs/implplan/SPRINTS.md`.
- Added a comprehensive document for Secret Leak Detection operations detailing scope, prerequisites, rule bundle lifecycle, enabling the analyzer, policy patterns, observability, troubleshooting, and references.

src/Scanner/__Libraries/StellaOps.Scanner.Surface.Secrets/AGENTS.md

@@ -20,11 +20,11 @@ Provide a unified secret access layer for Scanner, Zastava, and related services
 - Security guidance in `docs/security/redaction-and-privacy.md`
 
 ## Working Agreement
-1. **Status synchronisation**: update task state in both `docs/implplan/SPRINTS.md` and local `TASKS.md` whenever you start or complete work.
+1. **Status synchronisation**: update task state in both sprint file `/docs/implplan/SPRINT_*.md` and local `TASKS.md` whenever you start or complete work.
 2. **Security posture**: enforce least privilege, short cache TTLs, redaction in logs, and Authority scope checks where applicable.
 3. **Deterministic behaviour**: deterministic secret selection & failure modes; avoid random jitter unless documented.
 4. **Offline readiness**: support sealed-mode bundles; document required manifest formats and verification steps.
 5. **Testing**: add unit/integration tests for each backend, rotation scenario, and failure path; include air-gap fixtures.
 6. **Documentation**: keep `surface-secrets.md` current; collaborate with DevOps to update Helm/Compose/offline-kit instructions.
 
-- 1. Update task status to `DOING`/`DONE` in both `docs/implplan/SPRINTS.md` and the local `TASKS.md` when you start or finish work.
+- 1. Update task status to `DOING`/`DONE` in both correspoding sprint file `/docs/implplan/SPRINT_*.md` and the local `TASKS.md` when you start or finish work.